4 ms·

The focus of buildings should be: 1. Keeping dry and bulk water out/away. 2. Being as air tight as possible.† 3. Controlling vapour. 4. Being well-insulated

The focus of buildings should be: 1. Keeping dry and bulk water out/away. 2. Being as air tight as possible.† 3. Controlling vapour. 4. Being well-insulated. * https://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall https://www.buildingscience.com/documents/insights/bsi-001-t... † Air is exchanged in a controlled fashioned: filtered for pollen and other things, and then tempered with an HRV/ERV. Buildings do not need to 'breathe': * https://www.youtube.com/watch?v=CIcrXut_EFA https://www.youtube.com/watch?v=CIcrXut_EFA

abakker 6y ago
Certain building materials need to breath. Buildings built with green wood which has more moisture than ambient, and buildings with cast concrete will shed water vapor for some time. If this can be managed, it is fine. Additionally, through all insulation there is an internal temperature gradient. If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. This can happen in in humid climates with inadequate insulation - especially fiberglass where moisture can easily penetrate the fiberglass to reach the colder outside walls. I agree, though. Air tightness and continuous insulation coupled with well-engineered ventilation is best.
- throw0101a 6y ago
  > Certain building materials need to breath. As explained in the linked video, they actually need to dry. This does not need to happen to the outside environment. IMHO, using the two terms (dry/breathe) interchangeably is causing confusion, as each has certain connotations in many people's minds. The person in that video lives in Austin, Texas, and when he builds or renovates structures he has a stand-alone, whole-house dehumidifier designed into the HVAC system (the client can of course reject the suggestion): * https://www.youtube.com/watch?v=OKJnP_6uxcg https://www.youtube.com/watch?v=OKJnP_6uxcg > If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which, as explained in the first link (BSI-001), is why you want external insulation (if possible); some portion of the insulation being continuous is code in many places nowadays. That way the condensation occurs on the outside of the water/vapour control layer. Joe Lstiburek: * https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s This is harder to do with renovations, but is code in most places. In Ontario, Canada the code (IIRC) also specifics what minimum portion of the insulation that should be on the 'outside' of the vapour control layer: the colder the region the more has to be external, so that condensation happens on the outside of the structure. Having it 100% external is ideal, but would cause trade-offs in other aspects of the building, which may not be desirable. An example of such a structure: * During construction: https://www.youtube.com/watch?v=d8i-93ABo3I https://www.youtube.com/watch?v=d8i-93ABo3I * Finished: https://www.youtube.com/watch?v=hTwq-qUnr9I https://www.youtube.com/watch?v=hTwq-qUnr9I Sadly, last time I checked, there was still no mandatory air tightness test for new builds in Ontario.
  - abakker 6y ago
    Here in Boulder County, new BuildSmart regulations will require new and renovated structures to pass a "Blower Door Test" Does Ontario not have any of those requirements for commercial or residential? Agree on the continuous insulation. Very hard to do for Renovations. Fortunately in Colorado, it is so dry that the vapor barrier is slightly less important than in places like new england.
    - throw0101a 6y ago
      > Does Ontario not have any of those requirements for commercial or residential? Last time I checked it no air leakage testing is mandated: * https://www.barriersciences.com/blog/potential-changes-ontario-building-code https://www.barriersciences.com/blog/potential-changes-ontar... * https://www.reminetwork.com/articles/canada-wavers-on-airtightness-testing/ https://www.reminetwork.com/articles/canada-wavers-on-airtig... I'm not in the industry, so only know about the rough outlines through casual interest.
- MertsA 6y ago
  >Additionally, through all insulation there is an internal temperature gradient. If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which is a good benefit of spray foam insulation. Your insulation is your air barrier and even if there was moisture in the pores of some open cell foam, it's not going to cause issues.
  - poseva 6y ago
    Foam insulation has other problems, see for eg. thermal drift.
intrepidhero 6y ago
The problem I have with this is if #1 ever fails, and lets be honest, it will eventually, then #2 means you'll get mold and its game over. Heat transfer mechanisms, in order of amount of heat moved typically follow: conduction, convection, and radiation and should be addressed in that order while not ignoring moisture content. Mitigation strategies should default to passive measures. Or at least that's my plan if I ever get around to building a house.
- throw0101a 6y ago
  The order of importance is not the order in which they are layered: * https://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall https://www.buildingscience.com/documents/insights/bsi-001-t... If you wish to argue against Joe Lstiburek, a PhD who has been doing building science for probably over thirty years (both academic research and field work/consulting), go right ahead. He has taken failures into account because a good portion of his career has been studying / consulting on failures: * https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s
jchrisa 6y ago
The problem with buildings with windows that don't open, is that the windows don't open. What do you do if you want to open the window?
- throw0101a 6y ago
  You can windows that open, just make sure they are not single/double-hung or any kind that slides, as those leak a lot IIRC. Get casement windows, which open on hinges, and that tend to have levers to apply force against a seal/gasket. * https://en.wikipedia.org/wiki/Casement_window https://en.wikipedia.org/wiki/Casement_window
ggm 6y ago
How long for VOC purge post build, pre occupancy?
- MertsA 6y ago
  What he's suggesting is an ERV or HRV. You still get air exchange, as much as you want, but now you're passing that air through a heat exchanger and a "humidity exchanger" so you're not wasting all of that energy to condition that air. Another big benefit, now you don't have that moist outside air passing through fiberglass insulation batts in the walls working like growth media for mold. As far as VOCs, you can crank up the air exchange to something on par with what a leaky building would do naturally. Even if you didn't, VOC off gassing should be basically the same rate. It's not going to accumulate enough in the air to substantially change the amount slowly coming out of paint, carpet, drywall, etc. If the air exchange rate was e.g. half then that should almost double the VOCs in the air.
  - ggm 6y ago
    I would hope it's an exponential drop off, and you could even wedge doors open and drive ahead of things and then go back into a more passive house fully sealed state.
    - MertsA 6y ago
      That's not going to get it to come out of the material faster, that'll just reduce the amount in the air. You're still stuck waiting for it to permeate out of paint, carpet, adhesives, etc. You could increase ventilation to get the VOCs in the air to an acceptable level faster, but you're not substantially increasing the rate at which it's coming out of the materials.

abakker 6y ago

Certain building materials need to breath. Buildings built with green wood which has more moisture than ambient, and buildings with cast concrete will shed water vapor for some time. If this can be managed, it is fine. Additionally, through all insulation there is an internal temperature gradient. If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. This can happen in in humid climates with inadequate insulation - especially fiberglass where moisture can easily penetrate the fiberglass to reach the colder outside walls. I agree, though. Air tightness and continuous insulation coupled with well-engineered ventilation is best.

throw0101a 6y ago
> Certain building materials need to breath. As explained in the linked video, they actually need to dry. This does not need to happen to the outside environment. IMHO, using the two terms (dry/breathe) interchangeably is causing confusion, as each has certain connotations in many people's minds. The person in that video lives in Austin, Texas, and when he builds or renovates structures he has a stand-alone, whole-house dehumidifier designed into the HVAC system (the client can of course reject the suggestion): * https://www.youtube.com/watch?v=OKJnP_6uxcg https://www.youtube.com/watch?v=OKJnP_6uxcg > If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which, as explained in the first link (BSI-001), is why you want external insulation (if possible); some portion of the insulation being continuous is code in many places nowadays. That way the condensation occurs on the outside of the water/vapour control layer. Joe Lstiburek: * https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s This is harder to do with renovations, but is code in most places. In Ontario, Canada the code (IIRC) also specifics what minimum portion of the insulation that should be on the 'outside' of the vapour control layer: the colder the region the more has to be external, so that condensation happens on the outside of the structure. Having it 100% external is ideal, but would cause trade-offs in other aspects of the building, which may not be desirable. An example of such a structure: * During construction: https://www.youtube.com/watch?v=d8i-93ABo3I https://www.youtube.com/watch?v=d8i-93ABo3I * Finished: https://www.youtube.com/watch?v=hTwq-qUnr9I https://www.youtube.com/watch?v=hTwq-qUnr9I Sadly, last time I checked, there was still no mandatory air tightness test for new builds in Ontario.
- abakker 6y ago
  Here in Boulder County, new BuildSmart regulations will require new and renovated structures to pass a "Blower Door Test" Does Ontario not have any of those requirements for commercial or residential? Agree on the continuous insulation. Very hard to do for Renovations. Fortunately in Colorado, it is so dry that the vapor barrier is slightly less important than in places like new england.
  - throw0101a 6y ago
    > Does Ontario not have any of those requirements for commercial or residential? Last time I checked it no air leakage testing is mandated: * https://www.barriersciences.com/blog/potential-changes-ontario-building-code https://www.barriersciences.com/blog/potential-changes-ontar... * https://www.reminetwork.com/articles/canada-wavers-on-airtightness-testing/ https://www.reminetwork.com/articles/canada-wavers-on-airtig... I'm not in the industry, so only know about the rough outlines through casual interest.
MertsA 6y ago
>Additionally, through all insulation there is an internal temperature gradient. If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which is a good benefit of spray foam insulation. Your insulation is your air barrier and even if there was moisture in the pores of some open cell foam, it's not going to cause issues.
- poseva 6y ago
  Foam insulation has other problems, see for eg. thermal drift.

intrepidhero 6y ago

The problem I have with this is if #1 ever fails, and lets be honest, it will eventually, then #2 means you'll get mold and its game over. Heat transfer mechanisms, in order of amount of heat moved typically follow: conduction, convection, and radiation and should be addressed in that order while not ignoring moisture content. Mitigation strategies should default to passive measures. Or at least that's my plan if I ever get around to building a house.

throw0101a 6y ago
The order of importance is not the order in which they are layered: * https://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall https://www.buildingscience.com/documents/insights/bsi-001-t... If you wish to argue against Joe Lstiburek, a PhD who has been doing building science for probably over thirty years (both academic research and field work/consulting), go right ahead. He has taken failures into account because a good portion of his career has been studying / consulting on failures: * https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s

jchrisa 6y ago

The problem with buildings with windows that don't open, is that the windows don't open. What do you do if you want to open the window?

throw0101a 6y ago
You can windows that open, just make sure they are not single/double-hung or any kind that slides, as those leak a lot IIRC. Get casement windows, which open on hinges, and that tend to have levers to apply force against a seal/gasket. * https://en.wikipedia.org/wiki/Casement_window https://en.wikipedia.org/wiki/Casement_window

ggm 6y ago

How long for VOC purge post build, pre occupancy?

MertsA 6y ago
What he's suggesting is an ERV or HRV. You still get air exchange, as much as you want, but now you're passing that air through a heat exchanger and a "humidity exchanger" so you're not wasting all of that energy to condition that air. Another big benefit, now you don't have that moist outside air passing through fiberglass insulation batts in the walls working like growth media for mold. As far as VOCs, you can crank up the air exchange to something on par with what a leaky building would do naturally. Even if you didn't, VOC off gassing should be basically the same rate. It's not going to accumulate enough in the air to substantially change the amount slowly coming out of paint, carpet, drywall, etc. If the air exchange rate was e.g. half then that should almost double the VOCs in the air.
- ggm 6y ago
  I would hope it's an exponential drop off, and you could even wedge doors open and drive ahead of things and then go back into a more passive house fully sealed state.
  - MertsA 6y ago
    That's not going to get it to come out of the material faster, that'll just reduce the amount in the air. You're still stuck waiting for it to permeate out of paint, carpet, adhesives, etc. You could increase ventilation to get the VOCs in the air to an acceptable level faster, but you're not substantially increasing the rate at which it's coming out of the materials.